Nick Jonas tweets (very buff) picture of his abs

Jaclyn is an Idaho native who currently lives in Milwaukee. Having worked in radio, TV and as a newspaper reporter, she is an avid pop culture and news junkie. She also has a passion for photography and cooking (but is still learning to ...

Day made for 7 million Jonas Bros. fans

Nick Jonas was always the baby of the group, but not any more. Is the group worried they are growing up too fast?

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Get ready to forget everything you ever knew about Nick Jonas. The Jonas Brothers’ youngest member is officially all grown up.

The 20-year-old posted a photo of himself on Instagram Tuesday, and he is definitely not the child he was when he worked his way into teen girls’ hearts everywhere.

He tweeted the photo to almost seven million followers, which showed Jonas with his arm behind his head, which helped flex his (surprisingly big) bicep. He was also wearing Nike shorts that seemed to be precariously close to making the photo a scandal a la Geraldo Riviera.

The world of Twitter was abuzz with news of Jonas’ photo on Tuesday. The singer has been single since splitting from Australian pop star Delta Goodrem in February 2012, and has been obviously using his extra time getting in shape. He has been tweeting about his fitness goals since at least spring.

Jonas’ diabetes was diagnosed at age 13, but he is doing what he can to manage it. The singer was in Charlotte, North Carolina on Tuesday night for a concert with his brothers Kevin and Joe. He tweeted about the state and filming the movieCareful What You Wish For, which also stars Dermot Mulroney and Isabel Lucas.

Back in NC very nostalgic. @CWYWF wrapped two months ago already! Who's ready for the show tonight?!

Despite growing up, The Jonas Brothers are still going strong. They will be releasing their fifth studio album this year, but aren't worried they are outgrowing their fans.

"The fans that have been with us from those days are still growing up with us now," Kevin Jonas told the SpartanburgHerald-Journal in June. "People think like ‘Oh, they have 13-to-16-year-old fans.' Well, no, those 13-to-16-year-old fans from five years ago are now in their 20s, 18 to 24, and are all in college. So those fans are coming to the shows, still."